It is frequently desired to analyze is liquid to determine the presence and concentration of analytes such as minor constituents and/or contaminants. In many instances, several different tests may be run on one or more portions of a single liquid sample, to detect and measure different constituents. For man common tests, reagents are available that provide an almost instantaneous result by changing either hue or intensity of color in response to a specific constituent in the liquid. An example is a swimming-pool test kit, which typically provides from two to six different reagents that test for common factors such as chlorine or bromine content, pH, and hardness of the water.
However, such test kits conventionally require the user to fill a specific amount of water into a test container, add a specific amount of reagent, judge the intensity or hue of the resulting color against a reference chart by eye, and repeat the whole process for each test that it is desired to carry out, if the test results are not within is desired range, the user must then manually calculate the amounts of chemicals to add to the swimming pool to adjust its condition to the desired range. That is time consuming, messy, and not very accurate. The situation is even worse for a pool supply store, where the store staff are frequently asked for assistance by a pool owner whose pool chemistry has gone wrong in a way that the owner cannot himself correct. The store staff may then need to conduct a much larger range of tests, and to convert the results of the tests to quantities of various chemicals to be added to the pool.
Similar issues occur in other businesses and industries. For example, in brewing, trace constituents of the water used can not only directly affect the flavor and quality of the brewed beverage, but also affect the behavior of the yeast and therefore the success and result of the brewing process. Other businesses in which a battery of tests, have to be performed fairly frequently, so that similar issues occur, include aquaria, aquaculture, environmental monitoring, and maintaining boilers and coolers.
There is, therefore, a need for apparatus and methods that make it possible to test a liquid sample for several different properties, for example, for the presence or absence of several different analytes, in a single operation, with a minimum of mess, and to obtain the results of the tests automatically, without relying on human judgment.